Valorisation of polylactic acid (PLA) waste: A comparative life cycle assessment of various solvent-based chemical recycling technologies

To understand the environmental impacts of various chemical recycling solutions for handling end-of-life (EoL) post-consumer (PC) PLA waste, a comparative environmental assessment was conducted. A life cycle assessment (LCA) was applied the ISO standards 14040/44. The functional unit of the study was the treatment of one tonne PC-PLA waste. The four EoL scenarios investigated were: (1) hydrolysis, (2) alcoholysis using methanol, (3) alcoholysis using ethanol and (4) the direct incineration of PC-PLA waste. The scope of the study considers environmental impacts emanating from: (a) the collection and transport of the PC-PLA waste, (b) its pretreatment, (c) respective EoL treatment for the production of recyclates and (e) the substitution of conventional products with recyclates. The results show that all three chemical recycling technologies perform better from an environmental perspective as compared to the direct incineration of the PLA waste. In particular, the chemical recycling processes using alcoholysis show considerable environmental benefits across various impact categories such as global warming, acidification, eutrophication, ionising radiation, photochemical ozone formation, resource use (energy carriers; mineral and metals) and respiratory inorganics. On the other hand, the valorisation of PLA to lactic acid via hydrolysis shows the highest benefits concerning land use and water scarcity. In the case of potential impacts on ozone depletion, alcoholysis-using methanol performs worst. Through the results obtained and subsequent discussions, this study establishes the need for instituting a recycling strategy for PLA to create a resource-efficient future involving different sectors along the value chain.